Sulfur compounds



3,041,280 Patented June 26, 1962 3,041,280 SULFUR CQMPOUNDS Robert K. Smith, Springfield Township, Delaware County, and Charlotte S. Popofi, Ambler, Pa, assignors to E. F. Houghton & Co., Phiiadeiphia, Pin, a corporation of Pennsylvania No Drawing. Filed Sept. 29, 1958, Ser. No. 763,832 23 Claims. (Cl. 25233.6)

This invention relates to lubricating compositions, and more particularly, provides novel lubricating compositions comprising an oleaginous base and certain chlorinated aromatic sulfur compounds as further defined hereinafter, and means of making the same.

The novel lubricating compositions provided by this invention are uniquely effective as extreme pressure lubricants. There is a continuing demand in the lubricant industry for lubricants effective at increasingly higher loading pressures. With the development of improved lubricating compositions to meet this demand, the operational range of pressures has been greatly extended. Pressures initially denoted as falling in the extreme pressure range are now many times lower than the maximum which has been reached. To keep pace with engineering developments, however, it is essential that the upper opera tional pressure limit be advanced further than has been attainable hitherto. Thus for example, higher speed aircraft with larger power plants and changed structural design present stringent requirements for lubricants, for which the load carrying and wear properties of known lubricant compositions are inadequate. In such applications, anticipated loads of sliding surfaces such as rod ends, pulleys, screw jack actuators, hinges, gear boxes and oscillating spherical bearings may range as high as 100,000-150,000 p.s.i., with ambient temperatures from 65 F. to 600 F. The present invention is particularly valuable in that it provides compositions capable of effective lubrication under these severe conditions.

The requirements which extreme pressure lubricating compositions, must meet include not only lubricity under high loads, but also good temperature response and substantial absence of corrosiveness. Natural oils such as mineral oils are generally of restricted utility: the viscosity-temperature characteristics of even highly refined mineral oils are unfavorable where lubricants must be operative over a broad temperature range. Synthetic lubricants, such as silicones, polyesters, and the like, are available which do not have this defect; however, such lubricants are less desirable in other respects. Thus synthetic lubricants such as the silicones and polyesters are deficient in lubricity, and the silicones are also poor in wear properties. This inferior lubricity limits the pres sures at which such fluids can be employed; thus, a sili cone-based grease performs well in the ABEC NLGI bearing tester (criterion for high temperature service and boundary lubrication at low loads), but fails in the Navy Gear Test (higher loads). Moreover, these synthetic lubricant bases present a particular problem because they are only poorly responsive to treatment with additives. Mineral oils generally can be substantially increased in load-carrying capacity with a variety of extreme pressure additives. However, only a limited number of such additives are effective to improve the extreme pressure properties of silicones and like synthetic oleaginous bases, and only a restricted degree of response is produced. Furthermore, known extreme pressure additives tend to be corrosive, and this corrosiveness is especially evident when lubricant compositions containing such additives are employed at elevated temperatures. High temperature operation is frequently an accompaniment of heavy load conditions, so that corrosiveness in such circumstances forms an important consideration in determining the suitability of lubricant compositions. Accordingly, prior to the production of the compositions of this invention, it has been impossible to provide satisfactory lubricants for wide temperature range operation with extremely heavy loads.

It is an object of this invention to provide lubricating compositions of improved performance characteristics, with higher load-carrying properties than have been known hitherto.

A particular object of this invention is to provide novel lubricant compositions characterized by eflfective lubricity under advanced extreme pressure conditions at ultra high loads.

Another object of this invention is to provide novel extreme pressure lubricant compositions which are substantially free of corrosive qualities.

A further object is to provide a novel method of improving the extreme pressure qualities of an oleaginous base by adding certain chlorinated aromatic sulfur compounds thereto.

An additional object is to provide novel high-temperature, heavy load-carrying greases.

These and other objects, including the provision of novel compounds useful as extreme pressure additives and for other applications, will become evident from a consideration of the following specification and claims.

The novel lubricant compositions of this invention comprise an oleaginous base containing a chlorinated aromatic sulfur compound selected from the class consisting of pentachlorobenzenethiol, heavy metal salts of pentachlorobenzenethiol, pentachlorophenylmercaptoacetic acid, heavy metal salts of pentachlorophenylmercaptoacetic acid, and esters of pentachlorophenylmercaptoacetic acid.

The novel compositions of this invention are prepared by dispersing a chlorinated aromatic sulfur compound of the stated nature in an oleaginous base, as further described hereinafter.

The presently provided novel lubricant compositions exhibit unique qualities which make possible the effective lubrication of mechanical components operating under service conditions which are substantially more severe than it has been possible to employ advantageously hitherto. The loads which can be efi'ectively lubricated With the novel lubricant compositions of this invention extend up into a higher range than it has ever previously been possible to lubricate satisfactorily. Even under severe service conditions at high-temperature operating conditions, they exert a high load-bearing capacity while remaining substantially free of corrosiveness. A partic ular advantage of the present invention is that the stated aromatic sulfur compounds can be used to produce substantial improvements in the extreme pressure qualities of synthetic lubricants; when these additives are introduced in low concentration, they can produce as much as triple the unmodified load carrying capacity of such base fluids, thereby bringing synthetic base fluids of this nature into the lubricity range requisite for utility under ultra-high loads.

The chlorinated aromatic sulfur compounds employed in the practice of this invention as extreme pressure additives to oleaginous bases are characterized by the presence of a pentachlorophenylmcrcapto radical,

Ol O1 s,041,2so

One class of the stated compounds comprises pentachlorobenzenethiol and heavy metal salts thereof. Pentachlorobenzenethiol is itself very effective in producing compositions in accordance with this invention; su1prisingly, in view of the acidic qualities of aromatic thiols land in view of the usually pronounced corrosive qualities of chlorine compounds, pentachlorobenzenethiol is substantially non-corrosive, and may be used advantageously in lubricating compositions designed for use at elevated pressures and temperatures.

The heavy metal salts of pentachlorobenzenethiol have also been found to'be efficient extreme pressure additives for oleaginous bases. Lubricating compositions comprising the stated salts have good load-carrying properties and minimal corrosivity even at high temperatures. The metals, pentachlorobenzenethiol salts of which are employed as lubricant composition components in accordance with this invention, are heavy metals, by which are meant metals having a density of 4 or more. Particularly preferred in this connection are heavy metals of group II of the periodic table, including mercury, cadmium, and as the salt-forming metal of choice, zinc, and of group IV, especially tin and lead. Alternatively, the selection depending on such considerations as the reactivity and availability of the metals, there may be employed salts of 1 other heavy metals, such as those of group I, like copper, silver and so forth; of group III, like indium and thalhum; of group IV, like thorium; of group V, like antimony and bismuth; of group Vi, like tungsten and tellurium; and of the transition elements, like iron, cobalt, nickel and so forth.

As Will be appreciated by those skilled in the art, when a salt of a polyvalent metal with an aromatic thiol is formed, the arylmercapto radical of the thiol may satisfy all or less than all of the valences of the metal. Both partial metal salts and metal salts fully substituted by the stated arylmercapto radical are useful in the practice 'of the present invention. When the arylthiol salt is formed in aqueous solution for example, a basic salt may be produced in which one or more of the metal valences is satisfied by a hydroxide ion; other anions may alter- 'natively be introduced if desired, although this will usually require additional. manipulative steps without corresponding benefit. For practical purposes, in any case, anion radicals when present in the arylmercapto salts of heavy metals will usually be inorganic radicals and generally of relatively low molecular weight, as for example a halide ion such as .chloride, bromide or fluoride ion, or an oxygen-containing radical such as hydroxide or 'carbonate, bicarbonate or sulfate.

p The preparation of the stated salts can be effected, for example, by reacting a convenient salt of pentachlorobenzenethiol, such as the water-soluble sodium salt thereof, solution witha salt of the selected heavy metal to eifect a metathetical exchange of ions; or by other means known in the art for the preparation of aromatic thiolate metal salts. V

Illustrative of the stated heavy metal .salts are zinc pentachloroben zenethiolate, cadmium pentachlorobenzenethiolate, mercury pentachlorobenzenethiolate, copper pentachlorobenzenethiolate, silver pentachlorobeuzenethiolate, tin pentachlorobenzenethiolate, .lead pentachlorobenzenethiolate, thorium pentachlorobenzenethiolate, antimony pentachlorobenzenethiolate, bismuth pentachlorobenzenethiolate, tungsten pentachlorobenzenethiolate, cobalt pentachlorobenzenethiolate, nickel pentachlorobenzenethiolate, basic zinc pentachlorobenzenetbiolate, basic cadmium pentachlorobenzenethiolate, basic lead pentachlorobenzenethiolate, lead chloride pentachlorobenzenethiolate, tin sulfate pentachlorobenzenethiolate, and so forth.

As indicated hereinabove, compounds employed as extreme pressure lubricant additives in accordance with this invention may alternatively comprise substituted acetic acids including pentachlorophenylmercaptoacetic acid, heavy metal salts of pentachlorophenylmercaptoacetic acid, or pentachlorophenylmercaptoacetic acid esters. In the stated substituted acetic acids, the substituents on the alpha carbon atom of the acetic acid, besides the pentachlorophenylmercapto radical, will preferably be hydrogen atoms, but may alternatively comprise small alkyl substituents.

This series of compounds, as compared to the pentachlorobenzenethiol compounds discussed above, is particularly advantageous because these mercaptoacetic acid compounds are soluble in oleaginous bases, including synthetic lubricant fluids such as silicones. Accordingly, the additives of this group are readily dispersed in such fluids to produce lubricant compositions which are intrinsically stable to storage and handling.

The parent compound of this series, pentachlorophenylmercaptoacetie acid, is a preferred component of the lubricant compositions of this invention. It is highly etfective in raising the load-carrying capacity of oleaginous bases, and surprisingly free from corrosivity even at high temperatures. Homologs comprising oc-alkyl-substituted acetic acids such as u-(pentachlorophenylmercaptoja-a-methylacetic acid, a-(pentachlorophenylmen capto-u-ethylacetic acid, a-(pentachlorophenylmercapto)- a-isopropylacetic acid and the like are also effective to accomplish the objects of this invention.

Heavy metal salts of the stated acid are also useful in the practice of the present invention. In respect to this embodiment of the invention, essentially the same considerations apply as have been pointed out in the foregoing discussion with respect to heavy metal thiolate salts useful in the practice of this invention. Thus, the salt-forming metal will be a heavy metal having a density of 4 or more, such as those mentioned above in connection with the pentachlorobenzenethiolates. Any anion satisfying valences of the metal other than those taken up by the pentachlorophenylmercaptoacetyl radical, if present, will generally be an inorganic anion of low molecular weight, as set forth above in connection with the pentachlorobenzenethiolates, preferably a hydroxide ion. Preparation of the stated salts may be effected by means well known in the art, such as reacting penta chlorophenylmercaptoacetic acid or a salt thereof in solution with a hydroxide or other salt of a selected heavy metal. Illustrative of the salts of this nature useful in the practice of this invention are zinc pentachlorophenylmercaptoacetate, zinc a-(pentachlorophenylmercapto)-a-methylacetate, cadmium pentachlorophenylmercaptoacetate, mercury pentachlorophenylmercaptoacetate, copper pentachlorophenylmercaptoaceate, silver pentachlorophenylmercaptoacetate, tin pentachlorophenylmer captoacetate, lead pentachlorophenylmercaptoacetate, thorium w(pentachlorophenylmercapto)-a-ethylacetate, antimony pentachlorophenylmercaptoacetate, bismuth pentachlorophenylmercaptoacetate, tungsten pentachlorophenylmercaptoacetate, cobalt pentachlorophenylmercaptoacetate, nickel pentachlorophenylmercaptoacetate, basic 'zinc pentachlorophenylmercaptoacetate, basic zinc or- (peutachlorophenylmercapto)-a,a-dimethylacetate, basic cadmium pentachlorophenylmercaptoacetate, lead chlo. ride pentachlorophenylmercaptoacetate, tin chloride pentachlorophenylmercaptoacetate, zinc sulfate pentachlorophenylmercaptoacetate, and the like.

The pentachlorophenylmercaptoacetic acid derivatives found to be useful in the practice of this invention also include substituted acetic acid esters of the stated type. The nature of the ester radical may vary widely. The stated ester radical will be an organic radical, containing at least one carbon atom; and may comprise a hydrocarbon radical, such as an alkyl, cycloalkyl, aryl, alkaryl or aralkyl radical, or a hydrocarbon radical containing any of a wide variety of non-interfering substituents, such as halogen atoms, hydroxy radicals, carboxy radicals, sulfo radicals, alkoxy radicals, hydroxyalkoxy radicals, aryloXy radicals, cycloalkoxy radicals, sulfamoyl radicals,

mercapto radicals, acyl radicals such as an acetyl or benzoyl radical, cyano radicals and the like. A preferred class of esters for the present purposes comprises aliphatic esters such as alkyl, haloalkyl, and oxyalkyl including hydroxyalkyl, alkoxyalkyl and hydroxyalkoxyalkyl esters containing up to 8 carbon atoms; the effectiveness of these esters as lubricant additives has been observed to diminish with increasing chain length, and when the ester radical contains above about 8 carbon atoms, the esters are not of the potency required to produce a degree of lubricity of the unusually high order of magnitude which may be provided in accordance with this invention. The stated aliphatic phentachlorophenylmercaptoacetic acid esters, so far as is known, are new compounds which are provided by this invention.

The preparation of the stated pentachlorophenylmercaptoacetic acid esters can be effected by conventional procedures for an esterification of an acid with an alcohol, such as reaction of the acid and alcohol in the presence of an acidic or basic catalyst, or by other means adapted for ester synthesis. Illustrative of the stated esters provided by this invention are alkyl esters such as methyl pentachlorophenylmercaptoacetate, ethyl pentachlorophenylmercaptoacetate, propyl pentachlorophenylmercaptoacetate, isobutyl pentachlorophenylmercaptoacetate, Z-ethylbutyl pentachlorophenylmercaptoacetate, amyl pentachlorophenylmercaptoacetate, neopentyl pentachlorophenylmercaptoacetate, octyl pentachlorophenylmercapto acetate, methyl w(pentachlorophenylmercapto)amethylacetate, methyl a-(pentachlorophenylmercapto)axpropylacetate, n-butyl a-(pentachlorophenylmercapto)-aethylacetate Z-ethylhexyl a-(pentachlorophenylmercapto) a-methylacetate and so forth. Carbocyclic esters useful in the practice of this invention comprise cycloalkyl esters such as cyclopentyl pentachlorophenylmercaptoacetate, cyclohexyl pentachlorophenylmercaptoacetate, and 1- methylcyclohexyl pentachlorophenylmercaptoacetate, aryl and alkaryl esters such as phenyl pentachlorophenylmercaptoacetate and tolyl pentachlorophenylmercaptoacetate; and aralkyl esters suchas benzyl pentachlorophenylmercaptoacetate. Ilustrative of the presently provided esters of pentachlorophenylmercaptoacetic acid which may be employed in the practice of this invention wherein the ester radical is a hydrocarbon radical containing non-interfering substituents are oxyalkyl esters such as 2-hydroxyethyl pentachlorophenylmercaptoacetate, 3-hydroxypropyl pentachlorophenylmercaptoacetate, 2-(ethyloxy)- ethyl pentachlorophenylmercaptoacetate, 2-(2 hydroxyethyloxy)ethyl pentachlorophenylmercaptoacetate, 2-butoxyethyl pentachlorophenylmercaptoacetate, and 2-hydroxyethyl a-(pentachlorophenylmercapto)-a-methylacetate; and haloalkyl esters such as 2-chloroethyl pentachlorophenylmercaptoacetate, 3 -chlorophenyl pentachlorophenylmercaptoacetate, 4-chlorobutyl pen-tachlorophenylmercaptoacetate, o-bromohexyl pentachlorophenylmercaptoacetate, 2-chl0rooctyl or-(pentachlorophenylmercapto)-u-methylacetate, and so forth. Illustrative of other types of presently useful esters are 2-carboxyethyl pentachlorophenylmercaptoacetate, 4-sulfamoylphenyl pentachlorophenylmercaptoacetate, 4-cyanopentyl pentachlorophenylmercaptoacetate, benzoylmethyl pentachlorophenylmercaptoacetate, Z-mercaptoethyl pentachlorophenylmercaptoace-tate, 4-acetylbutyl pentachlorophenylmercaptoacetate, 2 -carboxyethyl a-(pentachiorophenylmercapto)-a-methylacetate, 2-sulfoethyl a-(pentachlorophenylmercapto)-a-propylacetate, and the like.

The lubricant compositions provided in accordance with this invention will comprise an oleaginous basic stock compounded with one or more of the pentachlorophenylmercapto radical-containiug compounds described above.

The chlorinated aromatic sulfur compound employed in preparing extreme pressure fluid and grease-like lubricant compositions in accordance with this invention will be incorporated in amounts sufiicient to effect a substantial increase in load carrying capacity over that exhibited by the oleaginous base alone. Generally a minor amount of the stated additive as compared to oleaginous base is effective in achieving this improvement. The amount to be used may vary over a fairly wide range depending on the type of additive used, the nature of the oleaginous base, and the severity of the operating conditions under which the lubricant is to be actually used in service. In general, an increase in the amount of additive will produce an increase in the extreme pressure properties of the base, but for practical purposes, it usually will not be necessary to employ an amount of additive appreciably above about 15% by weight, based on the weight of the final composition. Ordinarily excellent results are achieved with con centrations on the order of between about 0.1% and 10% by weight. Generally at least about 0.05% of the additive will be employed.

The oleaginous base used in the compositions may be selected from a wide variety of natural or synthetic lubricating oils. Thus for example, natural oils can advantageously be employed in conjunction with the stated pentachlorophenylrnercapto compounds to provide extreme pressure lubricant compositions. Illustrative of such natural oleaginous bases are mineral oils such as naphthene and parafiin base oils; vegetable oils such as cotton seed oil and castor oil; animal and marine oils such as sperm whale oil, lard oil, blown fish oil and degras; and mixtures thereof. Of the natural oil bases, mineral oils are preferred. A typical mineral oil base for extreme pressure lubrication will be characterized by a viscosity of 35-350 Saybolt Universal seconds at 210 F., a viscosity index in the range of from 25 to 150, and a flash point of between about 275 and 600 F.

The synthetic oleaginous bases are of particular interest in connection with this invention, in that they offer more desirable properties than natural oils in some respects, and also in that only a limited number of additives are known which are effective to improve the extreme pressure properties of such lubricants to be substantial degree required, so that the particular benefits of this invention are of special advantage. Any of a wide variety of synthetic oleaginous bases may be employed to produce the compositions of this invention.

Polysiloxanes, also known as silicones, or silicone polymers, comprise one class of synthetic lubricant bases of commercial importance which may be improved in extreme pressure properties to a substantial degree by modification in accordance with this invention. .Polysiloxanes are compounds comprising essentially silicon atoms connected to one another by oxygen atoms. In liquid polyorganosiloxanes, or silicones, of the lubricating oil viscosity range, a preponderant number of the remaining valences of the silicon atoms are satisfied by the substitution thereon of organic radicals, attached by a carbon-tosilicon bond. Examples of such organic radicals are aliphatic radicals including alkyl radicfls such as methyl, ethyl, propyl, butyl, and so forth; alicyclic radicals such as phenyl, cyclohexyl, diphenyl, anthracyl, naphthyl, and so forth; aralkyl radicals such as benzyl and alkaryl radicals such as tolyl, xylyl, and so forth; and the like. Relatively common oils of this type are dimethylsilicone polymer, phenylmethylsilicone polymer, chlorophenylmethylsilicone polymer, and so forth. Of particular utility for lubricating purposes are silicones in which the silicon atoms are substituted by two different organic radicals, e.g. methyl and phenyl radicals. Especially effective properties have been obtained when the organic radicals substituted on the silicon atoms in the silicone polymers are in turn substituted by halogen atoms, especially chlorine atoms. Thus for example, the silicone may be substituted by chlorophenyl radicals such as dichlorophenyl, trichlorophenyl and tetrachlorophenyl radicals, other valences of the silicon atoms being satisfied by the hydrocarbon radicals such as methyl radicals or the like. As is well known in the art, the silicones intended for use as oleaginous bases will desirably contain an average of 'from 1.9 to 2.67 organic groups per silicon atom. Re- -maining valences, if any, of the silicon atoms may be sat- R(COOR (COOR Where R is an aliphatic or cycloaliphatic hydrocarbon radical of from 2 to 8 carbon atoms and R and R are the same or dilferent and are branched chain alkyl or alkyl-substituted cycloalkyl radicals of at least 4 carbon atoms. Such esters may be derived from succinic, maleic, pyrotartaric, glutaric, adipic, pimelic, suberic, azelaic,

,sebacic, pinic, thiopropionic or oxypropionic acids or the like, specific esters of this nature including for example di(1-methyl-4-ethyloctyl) glutarate, di(2-ethylhexyl) oxydibutyric acid, di(2-ethylhexyl) adipate, di(3-methylvbutyl) azelate, di-(Z-ethylhexyl) azelate, di-(2-ethylhexyl) sebacate, di(3,5,5-trimethy1hexyl) sebacate, di(2- ,ethylhexyl) maleate, di(methylcyc1ohexyl) adipate, 2-

ethylhexyl l-methylhexyl sebacate and the like. Alternatively, instead of derivation from a polycarboxylic acid, the polyester synthetic oleaginous bases may be produced by reacting a polyhydric alcohol with a monocarboxylic acid. Thus for example, a polyhydric alcohol such as ethylene glycol or pentaerythritol is esterified with an acid of relatively long chain length such as caproic, pelargonic, capric, lauric, myristic, palmitic or stearic acid, to produce a polyester of lubricating oil viscosity. Specific examples of such polyesters derived from polyols are pentaerythritol tetrapelargonate, pentaerythritol tetracaprate, pentaerythritol tetrapalmitate, pentaerythritol tetrastearate, ethylene glycol divalerate, diethylene glycol dicaprate, propylene glycol dicaprylate, and so forth. Another type of synthetic polyester lubricants which may be used as oleaginous bases in accordance with this invention will be complex esters obtained by esterifying a polycarboxylic acid with a diol, together with a monohydric alcohol and/or a monocarboxylic acid. Thus, complex esters which may be employed as oleaginous bases may be obtained by esterifying one mole of a dicarboxylic acid with 2 moles of a glycol and 2 moles of a monocarboxylic acid; or by esterifying one mole of a dicarboxylic acid with one mole each of a glycol, a monocarboxylic acid and a monohydric alcohol. Specific examples of suitable complex esters are the esters prepared from one mole of ethylene glycol, two moles of sebacic acid and two moles of Z-ethylhexanol; and the ester prepared from one mole of triethylene glycol, one mole of adipic acid, one mole of n-caproic acid and one mole of Z-ethylhexanol.

In addition to the above-mentioned classes of synthetic lubricating base stocks comprising types of present major commercial importance, there are a number of other oleaginous bases which can be used if desired in the practice of this invention. Thus for example, such lubricant bases may comprise hydrocarbon oils prepared by polymerization of unsaturated hydrocarbons. Polyethers of the nature of high molecular Weight polyoxyalkylene compounds, derived for example from ethylene oxide, propylene oxide and like substances, form another useful class of lubricant bases; similarly, there may be employed oleaginous bases of related structure, such as propylene oxide-tetrahydrofuran copolymers, and polyaryl ethers.

Besides the silicones discussed above, additional silicon derivatives of interest in this connection comprise silanes, organosilicates and disiloxanes such as hexaalkoxydisil- '8 oxanes of lubricating oil viscosity. Other synthetic oleaginous bases which may be mentioned include fluorocarbon oils such as perfluorinated petroleum oils; tetrasubstituted ureas; and esters such as dimethylcyclohexyl phthalate, trioctyl phosphate; and similar fluids adapted for lubricant applications.

Mixtures of oleaginous bases may sometimes be preferred to any single lubricant fluid. It has been found that certain advantages are possessed by base stock blends comprising silicone/polyester blends; and a blend of this composition as described hereinafter will form a preferred base stock for compounding with the stated chlorinated compounds to form the novel lubricant compositions of this invention.

In the context of severe operating conditions presenting demands for the ultra-high load bearing capacity of lubricating compositions obtainable in accordance with this invention, a form of lubricant composition which will be of particular importance will comprise a grease. To form greases, oleaginous bases as described above are compounded with a thickener effective to provide a gel structure and raise the dropping point of the composition. Any of a wide variety of thiekeners may be employed in the compositions of this invention.

One class of thickeners for formation of greases comprises soaps, that is, alkali metal salts of long chain fatty acids. There is a large number of such soaps which are effective for this purpose. Thus for example, lithium soaps of hydroxy fatty acids such as hydroxystearic acid, hydroxypalmitic acid, hydroxymyristic acid and so forth can be used as lubricant thickeners, alone or in admixture with naphthenic salts such as calcium naphthenate and the like. Another type of soaps effective for grease formation comprises Sodium soaps of carboxylic acids containing a high number of carbon atoms, such as the sodium salt of an eicosanoic acid the sodium salt of gadoleic acid, the sodium salt of montanic acid, the sodium salt of behenic acid and the like. The combination of a conventional soap thickener such as sodium salt of a hydrogenated fish oil acid with a salt derived from an aldehyde such as furfuraldehyde by the Cannizzaro reaction is illustrative of another group of thickeners within this general class. Soaps of the stated nature or any of a wide variety of other soap thickeners may be used in the compositions of this invention. In general, however, soap thickeners are not efiicient at substantially elevated temperatures; and where performance requirements call for greases operative at very high temperatures, other thickeners may be preferred.

Silica materials form another class of thickeners useful in grease formulation. Representative of such thickeners are silica aerogels, which may be treated in various ways, such as with reactive silicon compounds, to improve their grease-forming powers. A related type of thickener comprises a silicate, such as an organic derivative of bentonite clays.

A class of thickeners of particular importance in the preparation of lubricating compositions based on synthetic oleaginous bases comprises compounds containing an amide type linkage, including ureides, urethanes, al-

, lophanates, carbazides, carbazones and the like. Thickeners of this nature are particularly valuable when a I grease having high temperature stability is required. An

especially preferred class comprises a ureide of the formula RNHCONHR or RNHCONHRNHCONHR, where each R is an organic radical, preferably aromatic. Such ureides may conveniently be prepared by reacting an isocyanate with an amine. These thickeners may be synthesized separately and formulated with the oleaginous base to form a grease or, since the reaction of an isocyanate with an amine proceeds very readily, the components of the thickener may be reacted in situ in the oleaginous base; the latter is generally preferred. As illustrative of the isocyanates which may be employed to produce such thickeners may be mentioned aromatic iso- 9 cyanates such as p-chlorophenyl-isocyanate, p-tolylisocyanate, tolylenediisocyanate, p-biphenylylisocyanate (pxenylisocyanate), phenylisocyanate, p-carboxyphenylisocyanate, p,p'-diisocyanatodiphenyl, 2,5-dichlorophenylisocyanate and so forth, as well as alkyl isocyanates such as hexylisocyanate, 1,6-diisocyanatohexane, cyclohexaneisocyanate and so forth. Illustrative of amines which can be employed to produce the stated thickeners are aryl amines such as p-amino-biphenyl, benzidine, dianisidine, o-toluidine, p-aminobenzonitrile, p-phenylenediamine, mphenylenediamine, aniline, p-toluidine, and so forth; and alkyl amines such as 1,6-diaminohexane, 1,3-diaminopropane, diethylenetriamine, triethylenetetramine, hexylamine, dodecylamine and so forth. Examples of combinations of such isocyanates and amines which may be selected to produce thickeners for use in the presently provided lubricant compositions comprise a diamine such as benzidine with a monoisocyanate such as p-biphenylylisocyanate, in a 1:2 molar ratio; a diisocyanate such as hexylenediisocyanate with an amine such as aniline, in a 1:2 molar ratio; a diisocyanate such as tolylenediisocyanate with a mixture of amines such as aniline and pchloroaniline, in a molar ratio of 1:121, and so forth.

Instead of the above-mentioned thickeners, if desired, the lubricant compositions of this invention may be formulated as greases by the inco1poration of such thickeners as phthalimides, phthalocyanines, indanthrene, and so forth.

To formulate the lubricant compositions of this invention as greases, thickeners will be incorporated in proportions and by means usual in the lubricant art. Thus, the oleaginous base is preferably mixed with the thickeners under conditions of high shear, in a colloid mill, homogenizer or the like. The proportion of thickener to be used will vary very widely depending on the nature of the oleaginous base and the thickener. With the aryl-sub stituted urea thickeners, silicone polymer oils are general- 'ly thickened to grease consistency by the addition thereto of 5 to 70% and preferably to about to about 50% of the thickener by weight. For the present purposes, a proportion of about -25% thickener has been found satis factory in such a system, where the thickener employed was a mixed ureide prepared by reaction of a single aromatic diisocyanate with a mixture of two aromatic amines, reacted in situ in the oleaginous base. It is to be appreciated that with different thickeners and oleaginous bases, these proportions will be varied appropriately, as is well understood in the art.

The compositions of this invention may also comprise other property-modifying components such as antioxidants, pour point depressants or viscosity improvers, antifoaming agents or the like. Antioxidants which may be employed may be selected for example from alkyl phenols such as 2,4,6-trimethylphenol, pentamethylphenol, 2,4,6- tri-tert-butylphenol and the like; aminophenols such as benzylaminophenol; amines such as dibutyl-phenylenediamine, diphenylamine, phenyl-beta-naphthylamine, phenothiazine and dinaphthylamine; metal salts such as iron octoate; and so forth.

The invention is illustrated but not limited by the following examples.

EXAMPLES IIII These examples illustrate preparation of the pentachlorobenzenethiol heavy metal salts employed as extreme pressure additives in accordance with this invention.

(1) The Zinc salt of pentachlorobenzenethiol Was pre pared by reacting 30.6 parts of sodium pentachlorobenzenethiolate with an ammoniacal zinc chloride solution containing 7.5 parts of zinc chloride. A 97% yield was obtained. The zinc salt sublimes with some decomposition at about 350 C.

(II) The corresponding cadmium salt was prepared similarly by reaction of 30.6 parts of sodium pentachlorobenzenethiolate with an ammoniacal cadmium chloride solution containing 11.5 parts of CdCl Cadmium pentachlorobenzenethiolate sublimes with decomposition at about 350 C.

(III) For the preparation of the lead salt of pentachlorobenzenethiol, 30.6 parts of sodium pentachloro- .benzenethiolate were reacted with an aqueous solution containing 16 parts of lead acetate.

EXAMPLES IV-X Ester Recrystallized from M.P. 0.

Methyl Methanol 91 C.

Ethyl Petroleum ether"- 83 C.

Isopropyl do 83 C.

2-ethylbuty1 do 1. 30-34 C.

2-ethylhexyl None Liquid at room tempera- Monoglycol Toluene". 204 C 4-chloro-1-butyl. None Not purified.

EXAMPLES XI-XIII These examples illustrate preparation of the heavy metal salts of pentachlorophenylmercaptoacetic acid useful in preparing the lubricating compositions of this invention.

(XI) The Zinc salt of pentachlorophenylmercaptoacetic acid was prepared by reacting an aqueous solution containing 36.3 parts of the sodium pentachlorophenylmercaptoacetate with an ammoniacal solution of 13.6 parts of zinc chloride. An 87% yield was obtained.

(XII) The cadmium salt was obtained in a 95% yield using essentially the same procedure as described for the zinc-salt, by reaction of 36.3 parts of sodium pentachlorophenyhnercaptoacetate with 11.5 parts of cadmium chloride.

(XIII) The lead salt of pentachlorophenylmercapto acetic acid was prepared by reacting an aqueous solution of the 36.3 parts of corresponding sodium salt with a 2% solution of 18 parts of lead acetate. The lead salt was obtained in the yield of approximately 90%.

EXAMPLES XIV-XXXI These examples illustrate the improvement in properties of base fluids which can be obtained using the additives of this invention.

The lubricant compositions and base fluids were tested for their lubricity properties on a Shell 4-ball extreme pressure tester, which comprises a device for holding three rigidly clamped /2 inch metal balls submerged in a lubricant in a metal cup. A fourth rotating ball of the same diameter is then pressed into contact with the three stationary balls by an adjustable floating arm attached to .a. spindle rotating at approximately 1750 rpm. The tests were run at ambient temperatures at increasing loads until seizure and welding of the balls was observed to occur. The contact points on the three stationary balls Where they are rubbed by the rotating ball have formed a circular scar at this point, the diameter of which is a measure of the wear properties of the lubricant.

The following tables present the data obtained in this test and illustrate the eifectiveness of the additives employed to produce the compositions of the present invention, in a variety of base fluids.

flash point 575 F.; identified as DC 550.

Table I INOIPIENT WELD POINT, SHELL 4-BALL E. P. TEST Avg. Corr. Example Base fluid Additive, percent Load, wear scar load, kg. 'am., kg.

XIV Polymethylphenyl silicone 1 126 3.13 17. 6 XV do POBT, 2% 224 37 XVI do 1 PCPMAA, 2% 158 2. 36 31. XVII Chlorinated polymethylphenyl silicone 2 126 2. 32 23. 8 XV do 2 316 2. 20 85. 4 XIX d0 2 355 1. 23 100 X (10 112 2.48 19.0 XXI do 3 PCB'I, 2% 200 2. 27 45.0 X Polyester L- 89 2. 75 12. 2 XXIH ...do 4 PCPMAA, 3% 158 3. 43 22 XXIV- Didodeoyl dioctyl silane 56 2. 5 XXV PCBT, 3% 112 2. 45 19 XXVI- Didodecyl diphenyl silnne u 79 2. 7 11 XXVII. o Zn POBT, 3%--- 158 2. 3 32 XXVIII--. Octadecyl trideeyl si1ane. 79 2. 55 11 XXI clo Zn lOB'I; 3%.-." 178 2.12 41 XXX Hexa (2ethyl-hexoxy) siloxane 79 2.27 13 XXXL... do Zn PCBT, 3%--- 251 2.05 68 Midland, Mich, kinematic viscosity F., ASTM cell; pour point -58" F.;

'- A chlorinated polymethylphenylsilicone supplied by Dow Chemical 00., which, on

thermal decomposition, yields p-dichlorobenzene; viscosity, 9.0 cs. at 210 F., 52.6 cs. at 100 F., evapn. loss -26% in 22 hrs. at

400 F., ASTltl cell; identified as DC 4140.

. a A chlorinated polymethyiphenylsilicone supplied by General Electric viscosity 22.8 cs. at 200 F., 61.6 cs. at 10 evapn. loss in 6.5 hrs F.; identified as GE 81400 and also known as Versilube F-50.

00., Schenectady, N.Y.; kinematic at 400 F., ASTM cell; flash point 4 A polyester in the lubricant viscosity range, supplied by Emery Industries, Inc, Cincinnati, Ohio, and reputed to be pentaerythritol tetrapelargonate; viscosity 4.94 cs. at 210 F., 23.97 cs. at 100 F.; evapn. loss 14.6% in 22 hrs. at 400 F., ASTM cell; pour point 66 F.; flash point 515 F.; fire point 575 F.; identified as polyester 3137B.

=- Pcntachlorobenzenethiol. Pentachlorophenylmercaptoacetic acid. I Zinc pentachlorobenzenethiolate.

EXAMPLES XXXlI-XXXIII These examples illustrate the effect of the present additives in increasing the lubricity of greases.

' tion of silica-thickened greases with this product, a kettle was charged with the quantity of oleaginous base to be thickened, such as a silicone polymer. The silica thickener, in an amount equivalent to 15% by weight of the oleaginous base, was added to the fluid and the mixture stirred. Thereafter methanol, in an amount equal to 40% by weight of the thickener, was added gradually and the resulting fluid product passed through a Morehouse mill five times at 0.002 inch. Any solvent methanol remaining in the grease after milling is eliminated by a final heating; after which the desired extreme pressure additives are milled innto the grease.

The following data illustrate the improvement in properties which may be obtained by the use of the additive of this invention when the grease is thickened with a silica thickener. In this test the oleaginous base was the polymethylphenylsilicone of Examples XIV-XVI, thickened with 15% of the above mentioned silica thickener. The test procedure was the Shell 4-ball extreme pressure test described above.

The values given under the heading MHL in the foregoing table are the values calculated for the Mean Hertz Load of the greases, which is a measure of the ability of an olcaginous material to lubricate under ultra-high loads. The Mean Hertz Load is a value calculated from data measured by the Shell 4-Ball Extreme Pressure Machine and provides an index of load-carrying ability which combines the maximum load which can be imposed directly upon the lubricant as well as the wear scar diameters, which are observed during the course of the test. It is calculated as described in specification MIL-G-71l8.

EXAMPLES XXXlV-LIII These examples illustrate the effect of the present additives in increasing the load-carrying properties of arylsubstituted urea thickened greases.

Greases thickened with aryl-suhstituted ureas were prepared by dissolving the diisocyanate in a portion of the base fluid, dissolving the selected amine reactant in the l3 remainder of the fluid, and reacting the isocyanate with the amine reactant by mixing the two solutions at elevated temperature. Thus, to prepare greases employed in the tests discussed below, ditolylene diisocyanate was dissolved in about 30% of the selected base fluid and equimolar portions of p-chloroaniline and p-toluidine were dissolved in the remainder of the fluid in an amount such as to provide stoichiometric proportions of the diisocyamate and of the amines. Generally the quantities of these reactants were selected to provide between about 15 and about 25%, by weight in the grease, of the arylsubstituted urea product thereof, which in the case of the stated reactants, is 4-[3 (p-chlorophenyl)ureido]-4'- [3-(p-tolyl)ureido]-3,3-dimethylbiphenyl. After reaction had occurred, the resulting grease was cooled, passed once through a Morehouse mill at 0.002 inch, heated 4 hrs. at 450 F, again cooled and remilled. The selected extreme pressure additive is then milled into the grease.

In the following table are presented Mean Hertz Load values for an aryl-substituted urea thickened grease in which the oleaginous base comprised the polymethylphenylsilicone of Examples XIV-XVI.

Table IV gives the Mean Hertz Load values for greases based on the chlorinated polymethylpheuylsilicone of EX- amples XVII-XIX.

Table IV Example Additive Per- MHL cent XXXIX- a None 30 XL Pentachlorobenzcnetliiol 3 50 XLI Zinc pentsehlorobenzenethiolate. 1. 5 36 XLTT dn 3 53 XLIII do 6 77 XLIV Lead pentachlorobenzenethiolate 3 54 XLV Pentachlorophenylmereaptoacetic acid 3 72 XLVI do 3.5 94 XLVII Methfiylc pentachlorophenylmercapto- 3 53 ace a e. XLVIII ISOPIJDtYI pentaehlorophenylmereapto- 3-6 47 ace a e. XLIX Z-ethylbutyl pentachlorophenyl- 3 40 mercaptoacetate. L do 6 G3 LI 4-chloro-1-hutyl pentachlorophenyl- 3 48 mereaptoacetate. LII Zinc pentachlorophenylmercaptoacetate 3 47 LIII Lead pentachlorophenylmercaptoacetata 3 54 As will be observed by a consideration of the fore- 314 additives provided by this invention produces a substantial increase in the Mean Hertz Load of the greases; and indeed, with 3.5% of pentachlorophenylmercaptoacetic acid this value is better than tripled for the grease based on the chlorinated polymethylphenylsilicone, which even initially has a relatively high value for this figure.

EXAMPLES LIV-LXXIV As mentioned in the preceding discussion, experiments conducted in the course of the studies leading to the present invention have demonstrated that certain unexpected improvements in the load-carrying ability of lubricant compositions can be achieved by the use of oleaginous base blends as distinguished from single oleaginous bases. More particularly, blends of silicone lubricant fluids with ester lubricant fluids have been found to provide oleaginous bases with the good wear properties of ester synthetic lubricants combined with the superior load-carrying capacity of silicone fluids, and under certain circumstances preserving the good viscositytemperature characteristics of silicone fluids. With the stated blends, the load carrying capacity of the lubricant compositions thereby provided may initially be quite high; the values can, however, be still further improved by introducing the extreme pressure additives of this invention into the blended oleaginous bases. This is demonstrated by the data presented in the following tables, giving results obtained from greases prepared with the indicated oleaginous bases and thickened to a grease by introduction of the aryl-substituted urea thickener of Examples XXXIV-LIII, in an amount of about 20%.

Table VII presents data for greases comprising a polyspectively, as the oleaginous base, the polymethylphenylsilicone of Examples XIV-XVI: the polyester of Example XXII-XXIII; and a blend comprising by weight of each of the stated bases.

Table V ESTIMATED MEAN HERTZ LOAD OF GREASES Example oleaginous base Additive Per- MHL cent LIV Polymethyl- 15 phenylsilieone. LV Polyester 20-30 LVI, Blend 26 .do Zine pentachloro- 6 62 benzenethiolate. do Zinc pentaehlorophenyl- 6 80 mercaptoacetate.

Table VI presents data for greases comprising respectively, as the oleaginous base, the chlorinated polymethylphenylsilicone of Examples XVII-XIX; the polyester of Examples XXII-XXIII; and a blend comprising 50% by weight of each of the stated bases.

Table VI ESTIMATED MEAN HERTZ LOAD OF GREASES Example oleaginous base Additive Per; MHL

cen

LIX Chlorinated polymethylphenylsilicona. 30 LX Polyester 20-30 LXI Blend 35-40 LXIL- do Pentachlorobenzenethiol 3 53 LXIII o. Zine pentachlorobenzenethio 3 58 LXIV do do 6 68 LXV (in Cadmium pentachlorobenzenethiolate. 3 48 LXVI do Pent-aclllorophenylmercaptoacctic acid 3 72 Zinc pentachlorophenylmercaptoacetate 3 52 Cadrrtuttlm pentaehlorophenylmereapto- 3 ace a e. Zinc pentachlorobenzenethiolate 3 LXIX do and 77 Pentachlorophenylmercaptoacetic acid 3 Table VII presents data for greases comprising a poly- "methylphenylsilicone base fluid characterized by a kinematic viscosity of 11.8 cs. at 210 F. and 33.2 cs. at 100 F.; pour point --85 F.;flash point 535 F.; supplied by Dow Chemical Co., and identified by the supplier as DC 4039. Blend A comprised a mixture of 50% by weight, each, of the stated polymethylphenylsilicone and the polyester base of Example XXILXXHI. Blend B comprises a mixture of 75% by weight of the stated polymethylphenylsilicone, and 25% of the polyester base of Examples XXII-XXIII. Blend C comprised a mixture of 37.5%, by Weight, of the stated polymethylphenylsilicone; 37 .5 by weight, of the chlorinated polymethylphenylsilicone of Examples XVII-XIX; and 25%, by weight, of the polyester of Examples XXII-XXEH.

Table VII ESTIMATED MEAN HERTZ LOAD OF GREASES EXAMPLE IJQCV This example presents detailed test data for a typical lubricating composition provided in accordance with this invention.

The thickener employed in producing the grease, test data for which follow, comprised 17%, by weight of the grease, of an aryhsubstituted urea thickener prepared by reacting ditolylene diisocyanate with p-chloraniline and p-toluidine in situ in the oleaginous base fluid by the procedure of Examples XXIV-LIII. The oleaginous base used in this grease comprised a 50:50% by weight blend comprising respectively the chlorinated polymethylphenylsilicone lubricant fluid of Examples XVII-XIX and the polyester lubricant fluid of Examples XXII- )OGII. To this composition was added 3% by weight of zinc pentachlorobenzenethiolate as an extreme pressure 16 Materials Test Methods and the tests identified by MIT members are standard military test methods published by the Federal Government, as is the oil separation Federal Standard Method mentioned above. The Shell 4-ball test is conducted by substantially the same procedure as that described in a previous example hereinabove, with the difierence that in this test a steady load is applied rather than increasing loads.

EXAMPLES LXXVI-LXXVII The following examples illustrate that an improvement in extreme pressure properties is achieved by the present invention as embodied in compositions comprising a natural oil as the oleaginous base.

(LXXVI) A grease was prepared by thickening a naphthenic base mineral oil characterized by a viscosity of 725 Saybolt Universal seconds at 100 F. and a viscosity index of 85 with 8% by weight of a soap thickener comprising lithium hydroxystearate.

(LXXVII) Into a portion of this grease of Example LXXVI, there was incorporated 6% by weight of pentachlorophenylmercaptoacetic acid as an extreme pressure additive.

The Mean Hertz Load values of the mineral oil based grease with and without the stated additive were as follows:

EXAMPLES LXXVIII-LXXX These examples illustrate the excellent corrosion properties of the presently provided lubricant compositions.

Three percent of each of the indicated additives were incorporated separately into greases prepared with the chlorinated polymethylphenylsilicone of Examples XVII- XIX as the oleaginous base, thickened with the arylsubstituted urea described in Examples XXXlV-LIII. 4340 steel panels were cleaned and polished, then covered with a /s inch layer of grease and kept in a sealed jar at 400 F. for a period of 24 hours. The results are presented in the following table, in which the rating is a qualitative comparative value assigned on the basis of visual inspection of the panels, in which a higher figure corresponds to greater corrosion or attack on the panels.

Table VIII CORROSION TEST, 24 HOURS AT 400 F.

Weight Example Additive change of Rating Comments panel mg.

LXXVIII None 4 200 4 Surface corrosion. LXXLX Pentachlorophenyl-mercaptoacetic 301d--." 0 1 Light oxide stain. No pitting or corrosion. LXXX Zinc pentachloro-hcnzenethiolate 10 2 Purple heat stain. No pitting or corrosion.

:additive in accordance with the method of this inven- None.

52,100 steel balls. 10-40. 0651-1309.

Free

Mean Hertz G7118 Water washout MILG3278A Shell a-hall wear test 2 hours 1,200

r.p.m. 75 C Load, k Average scar diameter, mm Apparent viscosity in poises for 2 seconds ASTM method D1092- In the foregoing table, the test procedures described with the prefix AST M are American Society for Testing 15,000 at --45 F.

As will be seen from the foregoing data, the additives employed to produce lubricating compositions in accordance with this invention actually may reduce the corrosivity of the base greases, exerting a corrosion-inhibiting effect. By contrast, greases comprising the same oleaginous base in combination with a commercial extreme pressure additive are found to produce heavy corrosion within 24 hours at 400 F.

Similar results to those shown in Table VIII were obtained when the grease compositions of this invention were tested by Federal Standard Method 79l5319-T, run at relative humidity. Greases thickened with the aryl-substituted urea of Examples XXXIV-LIII comprising, respectively, the chlorinated polymethylphenylsilicone base of Examples XVII-XIX, and the blend of chlorinated polymethylphenylsilicone base fluid and polyester base fluid of Examples LX'I-LXIX were compounded with 3% of additives comprising zinc pentachlorobenzenethiolate, pentachlorobenzenethiol, pentachlorophenylmercaptoacetic acid, zinc pentachlorophenylmercapto- 17 acetate, and cadmium pentachlorophenylmercaptoacetate. The greases all gave a test rating of 2; which is an acceptable rating under the stated Standard Method.

While the invention has been illustrated with reference to various particular embodiments thereof, it is to be appreciated that modifications and variations can be made within the scope of the invention.

What is claimed is:

1. A lubricating composition consisting essentially of a lubricating oil and, as an extreme pressure additive, from about 0.05 to about 15% by weight of the total composition, of a chlorinated aromatic sulfur compound selected from the class consisting of pentachlorobenzenethiol, heavy metal salts of pentachlorobenzenethiol, pentachlorophenylmercaptoacetic acid, heavy metal salts of pentachlorophenylmercaptoacetic acid, and esters of pentachlorophenylmercaptoacetic acid.

2. The lubricating composition of claim 1 wherein the said lubricating oil is a synthetic lubricant fluid.

3. The lubricating composition of claim 1 wherein the said extreme pressure additive is pentachlorophenylmercaptoacetic acid.

4. The lubricating composition of claim 2 wherein the said synthetic lubricant fluid comprises a silicone.

5. The lubricating composition of claim 2 wherein the said synthetic lubricant fluid comprises a mixture of a silicone and a polyester within the lubricating fluid viscosity range, said silicone providing from about 50% to about 75% by weight of said mixture.

6. The lubricating composition of claim 2 wherein said synthetic lubricant fluid is a silicone, and wherein said extreme pressure additive is pentachlorophenylmercaptoacetic acid.

7. The lubricating composition of claim 2 wherein said synthetic lubricant fluid is a mixture of a silicone and a polyester within the lubricating fluid viscosity range, said silicone providing from about 50% to about 75% by weight of said mixture, and wherein said extreme pressure additive is pentachlorophenylmercaptoacetic acid.

8. A lubricating grease composition consisting essentially of a lubricating oil, from about 5% to about 70%, by weight of the total composition, of a thickener, and as an extreme pressure additive, from about 0.05% to about 15% by weight of the total composition, of a chlorinated aromatic sulfur compound selected from the class consisting of pentachlorobenzenethiol, heavy metal salts of pentachlorobenzenethiol, pentachlorophenylmercaptoacetic acid, heavy metal salts of pentachlorophenylmercaptoacetic acid, and esters of pentachlorophenylmercaptoacetic acid.

9. The lubricant composition of claim 8 wherein the said extreme pressure additive is pentachlorobenzenethiol.

10. The lubricating composition of claim 8 wherein the said extreme pressure additive is a heavy metal salt of pentachlorobenzenethiol.

11. The lubricating composition of claim 8 wherein the said extreme pressure additive is pentachlorophenylmercaptoacetic acid.

12. The lubricaating composition of claim 8 wherein 18 the said extreme pressure additive is a heavy metal salt of pentachlorophenylmercaptoacetic acid.

13. The lubricating composition of claim 8 wherein the said extreme pressure additive is an ester of pentachlorophenylmercaptoacetic acid.

14. The lubricating grease composition of claim 8 wherein said lubricating oil is a silicone fluid and said extreme pressure additive is pentachlorophenylmercaptoacetic acid.

15. The lubricating grease composition of claim 8 wherein said lubricating oil is a mixture of a silicone and a polyester within the lubricating tfluid viscosity range, said silicone providing from about 50% to about 75% by weight of said mixture, and said extreme pressure additive is pentachlorophenylmercaptoacetic acid.

16. A lubricating composition of claim 10 wherein the said heavy metal salt is a zinc salt.

17. The lubricating composition of claim 12 wherein the said heavy metal salt is a zinc salt.

18. A lubricating grease composition consisting essentially of a silicone fluid lubricating oil consisting of a silicone fluid, from about 5% to about by Weight of the total composition, of a thickener consisting of an aryl-substituted urea, and from about 0.05% to about 15 by weight of the total composition, of an extreme pressure additive consisting of pentachlorophenylmercaptoacetic acid.

19. A lubricating composition consisting of a lubricating oil and, as an extreme pressure additive, an amount which is at least about 0.05% based on the weight of the total composition, said amount being sufiicient :to produce extreme pressure properties, of a chlorinated aromatic sulfur compound selected from the class consisting of pentachlorobenzenethiol, heavy metal salts of pentachlorobenzenethiol, pentachlorophenylmercaptoacetic acid, heavy metal salts of pentachlorophenylmercaptoacetic acid, and esters of pentachlorophenylmercaptoacetic acid.

20. The lubricating composition of claim 19 wherein the said extreme pressure additive is pentachlorophenylmercaptoacetic acid.

21. The lubricating composition of claim 19' wherein the said lubricating oil is a synthetic lubricant fluid.

22. The method of lubricating which comprises interposing between load-bearing sliding surfaces, a composition as defined in claim 1.

23. The method of lubricating which comprises interposing between load-bearing sliding surfaces, a composition as defined in claim 8.

References Cited in the file of this patent UNITED STATES PATENTS 2,160,273 Loane et a1 May 30, 1939 2,216,751 Rosen Oct. 8, 1940 2,255,085 Prutton et al. Sept. 9, 1941 2,335,017 McNab et a1 Nov. 23, 1943 2,347,217 Prutton et a1 Apr. 25, 1944 2,849,479 Carmack et al. Aug. 26, 1958 2,877,261 Hardy et al Mar. 10, 1959 2,897,081 Dersch et al July 28, 1959 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N0. 3,041,280 June 26, 1962 Robert K. Smith et al-.

It is hereby certified that error appears in the above numbered patant requiring correction and that the said Letters Patent should read as corrected below.

In the heading to the printed specification, line 2, title of invention, for "SULFUR COMPOUNDS" read LUBRICATING COMPOSITION CONTAINING CHLORINATED,-'SULFUR COMPOUNDS column 6 line 38, for "be" read the 'column 14, line 32, for "VII" read V same column 14, lines 32 and 33, for "a polyspec tively" read respectively column 15, lines 8 and 9, for "comprises" read comprised column 18 lines 21 and 22 strike out "consisting of a silicone fluid".

Signed and sealed this 27th day of November 1962.

SEAL) fittest:

ZSTON G. O N m3 (0 DAVID L. LADD Lttesting Officer Commissioner of Patents 

1. A LUBRICATING COMPOSITION CONSISTING ESSENTIALLY OF A LUBRICATING OIL AND, AS AN EXTREME PRESSURE ADDITIVE, FROM ABOUT 0.05% TO ABOUT 15% BY WEIGHT OF THE TOTAL COMPOSITION, OF A CHLORINATED AROMATIC SULFUR COMPOUND SELECTED FROM THE CLASS CONSISTING OF PENTACHLOROBENZENETHIOL, HEAVY METAL SALTS OF PENTACHLOROBENZENETHIOL, PENTACHLOROPHENYLMERCAPTOACETIC ACID, HEAVY METAL SALTS OF PENTACHLOROPHENYLMERCAPTOACETIC ACID, AND ESTERS OF PENTACHLOROPHENYLMERCAPTOACETIC ACID. 